Centrifugal projectile fuze



April 1956 R. L. GRAUMANN ETAL 2,741,183

CENTRIFUGAL PROJECTILE FUZE 2 Sheets-Sheet 1 Filed May 26, 1945 gawc/rvfow IIJI/ R.L. Qr'auma W J Donahue, J1?

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CENTRJFUGAL PRGJECTILE FUZE Raymond L. Graumann, Alexandria, Va., and William J. Donahue, Jr., Washington, D. C.

Application May 26, 1945, Serial No. 596,068

1 Claim. (Cl. 102-79) (Granted under Title 35, U. S. (lode (1952), sec. 266) This invention relates to a fuze for an explosive shell or projectile adapted to be fired from a gun and exploded upon striking a target, in which means are employed for preventing the premature firing of the explosive charge until the shell has traveled a safe distance beyond the muzzle of a gun. More specifically, the invention relates to a new and improved fuze for a projectile in which the firing pin and rotor supporting the detonator are locked in safe position with respect to each other until the projectile has attained a predetermined speed of rotation during the firing of the projectile from a gun and the force of acceleration of the projectile has diminished to a value corresponding to the force of acceleration acting on the projectile at a safe distance from a gun after the projectile has been fired therefrom.

This invention provides new and improved means for preventing the premature explosion of the shell or projectile in or within the vicinity of a gun as the gun is fired in which a rotor supporting the detonator, and a firing pin adapted to explode the detonator are locked in safe position until the gun within which the projectile is arranged has been fired.

The principal object of the invention is the provision of new and improved means for preventing the premature firing of an explosive charge within a projectile during the transportation, handling, loading and firing of the projectile from a gun.

Another of the objects is to provide a new and improved device for maintaining the detonator and firing pin locked in a safe position as the projectile is tired from a gun until the acceleration of the projectile and the speed of rotation thereof about the axis of the projectile has reached a predetermined value.

Another object is to provide a new and improved fuze having means for preventing the premature firing of an explosive charge within a projectile in which the rotor supporting the detonator, and the firing pin are locked in a safe or unarmed position until the velocity of the projectile, after being fired from the gun, has reached substantially the maximum value and in which the rotor will remain in an unarmed position, and the locking means for the firing pin are maintained in a locked position by the setback force of the projectile during the travel of the projectile through the gun barrel.

A further object is to provide a new and improved fuze for an explosive projectile having means arranged therein for preventing arming and firing thereof until the projectile is shot clear of the gun, which is economical to manufacture, reliable in operation, and which possesses the qualities of durability and safety during handling and transportation.

Still other objects and advantages will be apparent from the following description taken in connection with the accompanying drawings, of which:

Fig. 1 is a view partially in elevation and partially in section of a projectile employing the fuze of the present invention according to a preferred embodiment thereof;

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Fig. 2 is an enlarged sectional view of the fuze showing the elements thereof in an unarmed position;

Fig. 3 is an enlarged sectional view of the fuze taken on line 3-3 of Fig. 2;

Fig. 4 is an enlarged sectional view of the fuze taken substantially at a right angle to Fig. 2;

Fig. 5 is a view similar to Fig.2 but showing the device in an armed or firing position;

Fig. 6 is a view of the fuze of Fig. 5 but taken substantially at a right angle thereto; and,

Fig. 7 is an end elevational view of the rotor block showing the rotor and setback block arranged therein.

Referring now to the drawings for a more complete understanding of the invention and more particularly to Fig. 1 thereof, there is shown thereon a shell or projectile indicated by the numeral 10 adapted to be secured in any suitable manner to a shell casing 11 having the usual explosive charge 12 arranged therein for the purpose of propelling the projectile from the shell casing and through the bore of the gun, as is well known to those skilled in the art. The projectile is also preferably provided with an annular sleeve 13 of material suitable for the purpose such, for example, as brass adapted to be engaged by the rifiing of the gun as the projectile is propelled outwardly therefrom by the firing of the explosive charge 12 within the shell casing 11 and thereby impart a rotary movement to the projectile about the axis thereof as the projectile moves through the bore of the gun. The projectile is thus adapted to be propelled along a predetermined trajectory and to spin or rotate continuously about its axis throughout the trajectory as the result of the rotary movement imparted thereto by the rifiing of the gun. The projectile has the usual bursting charge 14 arranged there,- in and may also be provided with a tracer charge as indicated by the numeral 15.

The fuze generally indicated by the reference character 16, comprises a leading end or nose 17 composed of any material suitable for the purpose such, for example, as zinc and is secured to the shell ill in any suitable manner, preferably by an externally screw threaded nipple 18 integrally formed with the nose and having screw threaded engagement with a screw threaded bore 19 provided in the end of the shell ill. The nose 17 is provided with an enlarged bore 21, a portion of which is screw threaded as at 22 and adapted to have screw threaded engagement with a magazine generally indicated by the reference character 23 and thus the magazine is secured within the nose and extends a predetermined distance 7 therein. The magazine is provided with an enlarged bore or recess 24 having a booster pellet 25 arranged therein and composed of any explosive suitable for the purpose but preferably of the type known in the trade as Tetryl. A reduced bore 26 is provided in the magazine in communication with the enlarged bore 24 and a booster lead-in charge of Tetryl indicated by the reference character 27 is arranged therein, and engages the booster pellet 25 to provide means for firing the booster pellet.

The booster pellet or charge 25 is prevented from shifting Within the bore 24 by a disk 23 composed of blotting paper or the like disposed against a shoulder 29 provided within the bore 24 and clamped in position by a steel disk 31 in engagement with a flange 32 provided on the magazine. It will be understood that the blotting disk 28 provides a cushion for the booster pellet and also prevents any shifting thereof within the bore 24 thus preventing premature firing of the charge, and the steel disk 31 provides a support for the disk 28 to prevent ripping or tearing of the blotting disk as the projectile is fired from a gun.

A rotor block generally indicated by the reference character 33 composed of any material suitable for the purpose such, for example, as aluminum is secured within he bore 21, one end thereof having abutting relation with espect to the magazine 23, and adjacent the other end hereof a shoulder 34 is provided adapted to engage a urface 35 formed Within the nose of the projectile. ,The

otor block 33 is provided with a reduced annular mem ter 36 integrally formed thereon which terminates in a educed member 37 adapted to extend into a circular well i8 provided in the nose and having the axis thereof aranged coaxially with the axis of the projectile. -A rotor r turret 3% composed of any material suitable for the urpose such, for example, as brass and an openng 41 extending therethrough is arranged within a recess 52 provided within the rotor block 33 and is adapted to rave rotative movement therein. Arranged within the pening 41 of the rotor is a compound detonator 43 :omprising a casing 44 having a plurality of explosive :harges arranged therein such, for example, as the azidc )riming charge 45, lead azide 46 and Tetryl 57. The .pecific gravity of the explosive charges is less than the pecific gravity of the surrounding material whereby a iynamic couple is produced by rotation of the shell'sufii zientto rotate the rotor into an armed position with the :xplosive charges in aiinement with the rotational axis of :he shell after the projectile leaves the muzzle of the gun. isshown especially on Figs. 2 and 4 of the drawings he rotor is held in safe position by a setback block 48 :ecured to the rotor in any suitable manner but pref- :rably by a shear pin 49 composed of metal suitable. for he purpose such, for example, as copper and adapted extend through registering openings 51 provided in the 'otor and setback block 48. The block 48 is arranged within a recess or runway 52 provided in the rotor block 1nd adjacent the recess 42 and is adapted to have sliding novement within the recess so as to shear the pin 49 by :hesetback force received as the projectile is fired thereby releasing the rotor for rotative movement within the recess 12 when a predetermined speed of rotation has been reached by the projectile and after the projectile has moved past the limits of the gun.

.It will be understood, however, that after the pin 49 ms been sheared in response to the setback force received 9y the setback 43 as the projectile is fired from the gun the rotor is released but, due to the setback force thereon, the rotor will bind against the wall of the recess 42 in such-a manner as to prevent rotation of the rotor therein until the setback force decays sulliciently to permit free rotation of the rotor. When this occurs the rotor will move to an armed position as best shown on Figs. 5 and 6 of the drawings and when the projectile has reached a maximum speed of rotation. As shown on the drawings, especially Fig. 7 thereof, the setback block 48 is provided with a chamfer or bevelled portion 53 adapted to engage a bevel surface 54 provided in one corner of the recess 52 whereby the rotor and setback block are prevented from being transposed during assembly, thus assuring firing ofthe detonator 43 after the rotorhas been moved to an armed position. V

.A bore 55 extends through the annular member 36 and the reduced extension 37 and communicates with the recess 42 and slideably disposed within the bore is a firing pin 56 having an extension or hammer member 57 composed of any suitable material such, for example, as Bakelite secured thereto. The hammer member 57 is adapted to drive the firing pin rearwardly through the bore 55 and into engagement with the detonator 43 in response to the crushing of the nose of the projectile as the projectile strikes the target. It will, of course, be understood that, if desired, the hammer member 57 may be made of the same material as the firing pin and, furthermore, the hammer member may be of integral construction. In accordance with a preferred embodiment of the invention the firing pin is composed of aluminum and .ithe hammer member 57 may be composed of frangible material suitable forthe purpose. such, foriexample, as Bakelite.

Theinvention, however, is not limited to this specific construction and, if desired, the firing pin and hammer may be of integral construction and composed of frangible material possessing the properties of Bakelite. The annular member 36 is provided with a pair of diametrically arranged apertures 53 within which is respectively disposed a pair of locking detents 59 adapted to be releasably maintained. in engagement with a reduced cylindrical portion 61 of the firing pin by a circular spring 62 encircling the detents and adapted to urge the detents yieldably and inwardly against the firing pin, a chamber 63 being provided within the nose 17 of sufficient size to permit the spring 62 to expand and thereby release the detents from the locking position thereof, as will be more clearly apparent as the description proceeds.

With the detents 59 in locking position as shown on Figs 2 and 3 ofthe drawings, the firing pin is maintained locked in safe or unarmed position and prevented from being brought into contact with the detonator by reason of the engagement of the inner portions of the detents 59 with a shoulder 64 on the firing pin.

The force resulting from the acceleration of the projectile in response to the expansion of the gases within the gun is applied in a direction along the path of travel of the projectile and is well knownas a setback force. This setback force decays to zero as the projectile leaves the muzzle of the gun.

As the projectile is propelled along the bore of the gun by .the explosion of the charge 12, the rifiing of the bore engages the sleeve 13 and imparts rotative movement of the projectile, thereby causing the detents to be spun rapidly about the a'xis'of the projectile and a centrifugal force to be generated thereby as is well known. This force is'of, sufficient strength to'overcome the tension in the spring 62 and to cause the detents 59 to move outwardly to an unlocking or armed position and clear of the path of travel of the firing pin.

On Figs. 5 and 6 of the drawings is shown the detents maintained in their unlocking or armed'position by centrifugal force during the travel of the projectile along the trajectory, the spring 62 being expanded into engagement with the cylindrical wall of the chamber 63 and, as

1 also shown on these figures, the pin 49 has been sheared due to the setback force as heretofore described and the rotor 33 has moved to armed position by centrifugal force, thus bringing the detonator into the path of travel of the firing pin. The projectile is thus armed when'the setback force of the firing pin 56 is insufficient to over come the centrifugal force of the locking members and the setback force of the rotor is also insufficient'to prevent free rotation of the rotor within the recess 33. Thus the firing pin 56 is in readiness to be driven against the detonator 43 by the force of impact received as the projectile strikes the target.

As the gun is fired the initial movement of the projectile away from the shell casing is a motion of translation and when the projectile has moved a predetermined distance within the bore-of the gun, the sleeve 13 engages the rifiing of the bore and rotation of the projectile is initiated thereby.

From the foregoing, it will be apparent that the setback force is applied to the projectile prior to the rotation movement thereof and thus the shear pin is seevred by the setback force at the instant the gun is fired, however the rotor will not move and the detents are effectively locked in locking position by the setback force before the centrifugal force comes into play, thereby providing an arrangement in which there is no possibility of prematurely arming the fuze until the projectile has safely cleared the gun.

The many advantages of the fuze constructed in accordance with the present invention will be readily apparent from the foregoing description, taken in connection "with the accompanying-drawings and, although a preferred embodiment of the device is illustrated and described, it is to be understood that changes in the details of construction and in the combination and arrangement of parts may be resorted to which fall within the scope of the invention as claimed.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

A fuze for an explosive shell having an impact nose secured to said shell, a casing secured within said nose, a booster charge arranged within said casing, a rotor block clamped within said nose by said casing, a rotor arranged within said rotor block and adapted to be rotated from an unarmed position to an armed position by centrifugal force as the shell rotates, a detonator secured within said rotor and adapted to fire said booster charge when the rotor is in said armed position, a channel in said rotor block adjacent said rotor, a mass disposed outwardly of said rotor and slidably mounted in said channel for movement in a direction parallel to the axis of the shell, a shear pin interconnecting said mass and said rotor for preventing rotation of the latter, said shear pin being adapted to be sheared by setbacli force as the shell is fired from a gun thereby to release the mass from the rotor and permit free rotation of the rotor to said armed position, a firing pin coaxially arranged within said nose and adapted to explode said detonator as the shell strikes a target, a stop member on said firing pin, a reduced cylindrical portion on the firing pin adjacent said stop member, a pair of detents adapted to be engaged by said stop member and thereby lock the firing pin in a safe position until the detents have been moved to an armed position in response to the rotative movement of the shell as the shell travels along a trajectory, means for yieldably urging said detents into engagement with said reduced cylindrical portion of the firing pin when the shell is in a state of rest, and frangible means secured to the firing pin for moving the firing pin into firing engagement with the detonator when the rotor is in said armed position and the shell strikes the target, said frangible means being adapted to be crushed sufiiciently to prevent the firing pin from being forcibly moved past said detents and into firing engagement with the detonator when the detents are in engagement with the firing pin and the shell is subjected to a shock sufiicient to crush said nose.

References Cited in the file of this patent UNITED STATES PATENTS 379,716 Nordenfelt Mar. 20, 1888 2,073,250 Morpeth Mar. 9, 1937 2,236,495 Birkigt Mar. 25, 1941 2,392,430 Teitscheid Jan. 8, 1946 2,392,884 Semple Jan. 15, 1946 FOREIGN PATENTS 257,335 Great Britain Aug. 27, 1926 34,024 France Oct. 23, 1928 49,790 France Apr. 4, 1939 

